Galvanized v.s. Stainless Steel Anchor bolts 1

[SKJ25POL]

I have designed 3/4"dia. anchor bolts w/ double nuts & washer(2 feet long/depth and 6" projection).

The anchor bolts are to be fasten a pre-engineed curved steel trusses to top of drilled piers.

I specified it (anchor bolts) to be galvanized, the contractor asking can stainless steel be an option.

- Will it be working same?
- Does it require diffrent design?
- Which perform better? What will be the diffrence?

I appreciate your feed bacsk.

Thank you,

 

[EngineeringEric]

Different material properties. Fy, FU, and E are all less for Stainless Steel. You may have to worry about galvanic action (Depends on environment and size of plates and everything). And they are usually more expensive.

IT can work, it isn't a calculation-less substitution typically

 

[JStephen]

Design will be different. For small quantities, custom fab, the SS may be less.

 

[SKJ25POL]

EngineeringEric, thank you very much for response. May I ask where I can get some basic information on galvanic action you stated?
Also, is it a problem using a stainless steel anchor bolt in combination of galvanized base plate?
I appreciate your feed back.

 

[EngineeringEric]

Not sure of the best reference, here is one.

http://www.bssa.org.uk/topics.php?article=89

There is a stainless steel forum here that has members far smarter than I in this matter. I think it is only a real concern in marine-ish environments. I believe water and other elements are require to create the anodic/cathodic problems. So assuming the 'weaker'
steel values are good, the environment is not a pool house and the mass of carbon-steel (galvanized) is great than stainless it should be ok. Again i am by no means an expert and have only been mixing and really designing with the two materials for a few years.

 

[SAIL3]

In addition to the items already mentioned, I was made aware recently that SS can corrode quicker than bare carbon stl in the absence of oxygen. Granted, there are few other conditions that must be present ie. moisture,etc. I had never suspected this before and would specify SS freely when corrosion was an issue.
I do not know that this condition will apply to anchor bolts, but I would investigate it further now that I was made aware of it. Galling is another issue with SS, especially if the ABs have to be pretentioned.Based on all these issues that have to be addressed, I would personally go the galvanized route. Hopefully, there may be someone on the forum that has more info on this.

 

[SKJ25POL]

Thank you every body for directions especially, EngineeringEric (Structural).

 

[TomDOT]

Like his post? Star it!

 

[desertfox]

Hi

This might be of interest:-

http://www.confast.com/articles/concrete-wedge-anchor.aspx

 

[dik]

TomDOT... good post by EE... starred.

 

[Jerehmy]

Make sure you specify a specific material. I always see "SS 304" or "SS 316" anchor bolts. There's many classes of SS anchor bolts and different ASTM's that are used.

On the galvanic corrosion, it depends how far away they are on the anodic index table. But you can have stainless steel bolts with aluminum framing without worrying about corrosion even though the anodic index chart says there will be damage.

Galvanic corrosion is a function of the areas of the material. The anode is the one that corrodes, so in stainless steel / aluminum interaction, the aluminum is the anode which has a large amount of material while the stainless steel is the cathode, which won't corrode.

Same with stainless steel bolts and carbon alloy steel. The stainless steel will be the cathode so you're good. As long as these aren't like waste water treatment plants, then you might want some gaskets separating everything because of constant water.

 

[TomDOT]

I've found the "area hypothesis" to be overly optimistic. When I see stainless bolts on galvanized pipe flanges near the ocean, there is typically accelerated loss of the galvanizing in a ring around the bolts, extending maybe 2cm from the bolt - no matter how big the area. Zinc/stainless is only a slightly wider couple than aluminum/stainless.

 

[Jerehmy]

TomDOT

The pipe is galvanized, so the area is very small compared to a pipe that is say, pure zinc? There cross sectional areas are probably similar since the galvanizing isn't very thick.

 

[TomDOT]

Surface area is more appropriate than volume when you are talking about anode/cathode ratios. Within a relatively small distance, as I mentioned above.

Once your 1-4 mils of zinc thickness is eaten away by galvanic action of the stainless bolt, you are pretty much done.

The carbon steel is exposed and has a much higher corrosion rate than the galvanizing.

 

[Ron]

Certain alloys of stainless steel are susceptible to chloride attack. Make sure the concrete has a very low chloride content.

Look carefully at the comparison of physical properties. Make sure strength, elongation and hardness are comparable.

 

[UcfSE]

See AISC Table 2-7 (14th) for fastener and base metal corrosion notes.